I am looking through the website for an answer to ground elder. Mine is growing in the flower beds amongst the plants and is very difficult to weed. If I use a chemical on them, will it kill the plants as well or are they resistant to it, if they are no

Ground elder is very difficult to controle if it is well established. The herbicide 'Roundup' is probably the best weedkiller for it but if you get one drop on another plant then that is dead also. If the infestation is light then you could have a small amount of roundup in an open container and, wearing a rubber glove, dip your fingers in the weedkiller and wipe them on the selected leaves.
The other way is to completely remove all your plants from the the bed and dig it over thoroughly, a major task. Even then, you probably have a hedge behind the herbacious border and a lawn in front of it. Ground elder roots could already be beneath each and will keep coming back to haunt you.

I'm an organic gardener and used to have a garden with the evil stuff. I resorted to digging ALL the plants up, potting up (which did them good actually, they were much healthier when I put them back!)

Then I systematically kept digging the bed up over and over and picked by hand even the tiniest shoot. It was worth it in the end and the only pieces that came back where the ones from next door's garden.

Good luck!